The idea that women who’ve been diagnosed with breast cancer and gone through treatment tend to gain weight has been hinted at by research and talked about extensively on the Breastcancer.org Discussion Boards.

The shock of a diagnosis, the disruption of your life, getting through and beyond surgery and radiation, the strain of relationships at home and at work, financial stress, and less physical activity all may contribute to weight gain. During chemotherapy, extra fluids and steroids together with less physical activity and a yearning for sweets all may lead to weight gain in many women. Other women find that starting hormonal therapy, such as tamoxifen or an aromatase inhibitor, leads to weight gain.

Still, doctors weren’t sure if any weight gain was related to menopause and the aging process (since many breast cancers are diagnosed near menopause) or if there were something about being diagnosed and treated for breast cancer that made women more likely to gain weight.

Women who are overweight have a higher risk of being diagnosed with breast cancer compared to women who maintain a healthy weight, especially after menopause. Being overweight also can increase the risk of breast cancer coming back (recurrence) in women who’ve been diagnosed.

By comparing a group of women at high risk for breast cancer who were diagnosed and treated for breast cancer with a very similar group of high-risk women who were not diagnosed, researchers found that the diagnosed women gained more weight over 4 years than the women who weren’t diagnosed.

All the women were part of another study, the Breast and Ovarian Surveillance Service cohort study. All the women were at high risk for breast cancer because of family history, and some of the women had abnormal BRCA1 or BRCA2 genes.

When the women joined the Breast and Ovarian Surveillance Study, they completed a baseline questionnaire that included information on their age, weight, menopausal status, level of physical activity, and any breast cancer diagnoses. They completed follow-up questionnaires every 3 or 4 years.

The researchers matched the diagnosed and non-diagnosed women by age and menopausal status and then figured out how much weight, if any, a woman gained by comparing her baseline questionnaire information to follow-up questionnaire information.

Of the 303 women who had been diagnosed with breast cancer:

179 had been treated within 5 years of filling out the baseline questionnaire

123 had been treated more than 5 years before filling out the baseline questionnaire

about 50% had been treated with chemotherapy

about 66% had been treated with hormonal therapy

About 68% of the women who had been diagnosed and about 72% of the women who hadn’t been diagnosed reported physical activity levels that met recommendations from the American Heart Association (150 minutes per week of moderate exercise or 75 minutes per week of vigorous exercise).

After adjusting for age, menopause, and other factors, the researchers found that the women who had been diagnosed with breast cancer gained more weight -- about 3.6 pounds on average -- than women who hadn’t been diagnosed with breast cancer.

Specifically:

Women who were diagnosed with breast cancer in the 5 years before they filled out the baseline questionnaire gained an average of 3.81 pounds more than women who hadn’t been diagnosed.

Women who were diagnosed with estrogen-receptor-negative breast cancer in the 5 years before they completed the baseline questionnaire gained an average of 7.26 pounds more than women who hadn’t been diagnosed.

Women who were treated with chemotherapy (with or without hormonal therapy) in the 5 years before they filled out the baseline questionnaire were more than twice as likely to gain at least 11 pounds compared to women who hadn’t been diagnosed.

Women who took a statin while receiving chemotherapy gained about 10 pounds more compared to non-diagnosed women who took a statin, as well as diagnosed and non-diagnosed women who didn’t take a statin.

On the other hand, women who:

were diagnosed more than 5 years before they filled out the baseline questionnaire

were treated with hormonal therapy for hormone-receptor-positive disease

were treated with chemotherapy more than 5 years before they filled out the baseline questionnaire

were no more likely to gain weight than women who hadn’t been diagnosed.

"Our study showed that women diagnosed with breast cancer and those who received chemotherapy to treat their breast cancer gained more weight within the first 5 years of diagnosis and treatment than cancer-free women," said Kala Visvanathan, M.B.B.S., M.H.S., associate professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health, who is also director of the Clinical Cancer Genetics and Prevention Service at the Kimmel Cancer Center and lead author of the study. "This study highlights the need for physicians and their patients, including those with a family history of the disease, to pay closer attention to weight gain during and after treatment.

"We’re looking at biomarkers in urine and blood in the diagnosed women and the women who haven’t been diagnosed to look for biochemical changes that may be related to this higher weight gain,” she added.

The researchers plan to continue to follow all the women in the study to see how the women’s weight changes over a longer period of time.

There are dozens of studies that have shown that losing weight, exercising more, and eating a healthy diet improve the physical and mental well-being of people who’ve been diagnosed with breast cancer. People who make these changes also see positive changes in biomarkers (measurable characteristics in the body) linked to breast cancer risk and outcomes.

But as many of us know, losing weight can be hard and frustrating.

Still, it can be done with careful changes to your diet and regular exercise. The first thing to do is to talk to your doctor about a healthy weight for you based on your age, height, body type, and activity level. Then ask your doctor about a safe and sensible plan to lose weight specifically designed for you and your needs.

Once you have the OK from your doctor and a weight goal, you can create a healthy eating plan that meets your nutritional needs. You may want to talk to a registered dietitian about how to create a healthy eating plan that’s tailored to your specific needs and likes.

Some women say that it helps to think of eating well and exercising as important parts of their treatment plans. Remember to be nice to yourself; don’t punish yourself.

In the Breastcancer.org Nutrition section, the Eating to Lose Weight After Treatment pages can help you assess your weight and create a healthy eating plan. And the Breastcancer.org Exercise section can help you find a trainer and learn how to stick to an exercise routine.